This invention relates to modem architecture for communication lines. More particularly, this invention relates to modem circuitry used in connection with isolation systems for connecting to phone lines.
New generations of consumer appliances like set-top boxes, payphones, vending machines and other systems often require or prefer low-speed data modems. Such modems allow remote hosts to handle billing or other housekeeping functions, or permit xe2x80x9csmartxe2x80x9d vending machines to call for more supplies. Although typical microprocessor and digital-signal-processor (DSP)-based multimedia chips employed in set-top boxes and other systems are capable of implementing a low-speed modem, they would do so at an undesirable manufacturing complexity and expense.
Prior modem architectures typically included multiple integrated circuits for handling modem processing and communication line termination. In particular, one or more digital-signal-processor chips have been coupled to analog-front-end circuitry, which in turn has been connected to line termination circuitry across a transformer isolation barrier. Such modem architectures suffer from numerous disadvantages.
The present invention provides an improved modem architecture and associated method that integrate modem and line-isolation circuitry so as to achieve modem functionality and system-side isolation functionality on a single integrated circuit.
In one embodiment, the present invention is an integrated modem and line-isolation circuit including system-side circuitry capable of being coupled to an isolation barrier to communicate digital information through the isolation barrier and digital signal processing (DSP) circuitry integrated with the system-side circuitry, where the DSP circuitry having a modem processor for modem data and a digital processor for the system-side circuitry. In a more particular embodiment, the integrated modem and line-isolation circuit may have a communication interface that is operable as an asynchronous serial interface. The system-side circuitry may also provide system-side phone-line direct-access-arrangement functionality. Still further, the digital processor may include digital filters for digital data received across the isolation barrier from a communication line and a digital modulator for digital data transmitted across the isolation barrier to the communication line.
In another embodiment, the present invention is a combined modem and line-isolation system, including a line-side line-isolation integrated circuit, a system-side line-isolation integrated circuit, and digital signal processing (DSP) circuitry included within the system-side line-isolation integrated circuit, where the DSP circuitry has a modem processor for modem data and a digital processor for system-side circuitry. In addition, the line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit are capable of being coupled to an isolation barrier to communicate digital information with each other through the isolation barrier. In a more particular embodiment, the combined modem and line-isolation system has a communication interface that is operable as an asynchronous serial interface. Also, the line-side line-isolation integrated circuit may provide phone-line direct-access-arrangement functionality. Still further, the line-side line-isolation integrated circuit may include digital-to-analog conversion circuitry for digital data received through the isolation barrier from the system-side line-isolation integrated circuit and analog-to-digital conversion circuitry for analog information received from the communication line.
In yet another embodiment, the present invention is a combined modem and line-isolation system including a line-side line-isolation integrated circuit, a system-side line-isolation integrated circuit, digital signal processing (DSP) circuitry included within the system-side line-isolation integrated circuit, and an isolation barrier coupled between the line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit. The line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit communicate digital information with each other through the isolation barrier. And the DSP circuitry has a modem processor for modem data and a digital processor for system-side circuitry. In a more particular embodiment, the isolation barrier may utilize a capacitively isolated barrier. In addition, the isolation barrier may utilize at least one capacitor as an isolation barrier.
Still further, the present invention is a method for combining line-isolation and modem data processing including providing a system-side line-isolation integrated circuit capable of transmitting digital data across an isolation barrier and capable of receiving digital data across the isolation barrier; processing the digital data transmitted or received across the isolation barrier with a digital processor within the system-side line-isolation integrated circuit, and also processing the digital data transmitted or received across the isolation barrier with a modem processor within the system-side line-isolation integrated circuit. In a more particular embodiment, the method also includes converting analog information from the communication line to digital information before sending digital information across the isolation barrier and converting digital information received from the isolation barrier to analog information before sending analog information to the communication line.